I have written four posts on this blog (here, here, here, and here) about court opinions and articles addressing the issue of whether police should be required to obtain a search warrant before attaching a GPS device to a suspect's vehicle. Those opinions and articles dealt with the Fourth Amendment(and state counterpart) implications of such "unwarranted" behavior, but a new article in InformationWeek calls into question whether GPS data is reliable enough to be admissible as expert evidence.

While the U.S. Supreme Court has yet to weigh in on the constitutionality of warrantless GPS tracking, a more fundamental question may be whether GPSdata is reliable enough to be admissible in court.

According to the article, it likely is not. Claburn notes that:

Todd Glassey, chief scientist of Certichron, a time data trust service, and founder of the U.S. Time Server Foundation, argues that GPS devices can be easily jammed and that their data can be spoofed, particularly when tied to cellular systems -- as offender tracking bracelets may be.

He then notes that this isn't a novel concern because "[t]he U.S. Department of Defense has forbidden the use of L1 GPS -- the version of GPS available to civilians [and used by many law enforcement entities] -- for military purposes since 1998, owing to data integrity and security shortcomings."The article also cites to a research paper by member os the Los Almos National LaboratoryVulnerability Assessment team, which concluded that "Civilian Civilian Global Positioning System (GPS) receivers are vulnerable to attacks such as blocking, jamming, and spoofing."

All of this might come to a head with the D.C. Circuit's upcoming opinion in United States v. Jones, a case involving the warrantless placement of a GPS device on a suspect's car. In a technical brief submitted by Glassey in that case, he argued that

"The knowledge of the use of GPS test equipment to alter or affect the readings inside of GPS receivers has already made the jump from the technology community to the hacker community such that commercial products and general knowledge of how to spoof L1 GPS systems is available everywhere."